Carburetor



April 4, 1939. R, F BRACKE 2,152,951

CARBURETOR Filed Feb. 25, 1935 3 Sheets-Sheet l April 4, 1939.

Filed Feb. 25, 1935 3 Sheets-Shea?I 2 CARBURETOR ,Filed Feb. 25, 1935 3 Sheets-Sheet 3 MM N Patentedr Apr.. 4, 1939 UNITED STATES PATENT OFFICE l zusam,

cmumrron Robert F. Bracke, Chicago, Ill. Application Febrary z5, 193s, semina. 1.943

s claims.- (ci. ce1-s4) My'invention pertains to carburetors and is particularly concerned with a fuel-lift carburetor having two or more fuel injecting systems.

An object o fv my invention is to provide a carl buretorhaving an improved air valve.

Another. object is to` provide a carburetor having a plurality of air valves and improved means for preventing fluttering of these air valves.

VAnother object .is to provide a carburetor wherein the operation of the air valve is stabilized.

Another object is to provide a carburetor wherein the fluid passing 'therethrough is prel. vented from eddying. l

.-j Another object is to provide a carburetor wherein the fuel feed nozzle delivers at a point approximately in the region of highest suction, and wherein this point of delivery is so located N relative to the other parts of the carburetor as to prevent freezing of any of the operative parts.

Another object is to provide an improved carburetor which is simple and rugged in construction, eillcient and reliable in operation, and eco le nomical to manufacture.

Other objects and advantages will become ap# parent as the description proceeds.

In the drawings, l`Figure 1 is a top plan view of .a carburetor '0 embodying my invention;

Figure 2 `isa vertical section taken on the line 2--2 of Figure 1;

Figure 3 is a vertical section taken on the line 3-3 of Figure 1, and

Figure 4 is a diagrammatic view of a carburetor embodying my invention.

Referring to-the drawings. I have shownmy carburetor as comprising an upper castingfA and' a lower casting B secured together by bo ts Ill 40 and having. an airtight gasket I2 iirmly cl ped between the two castings'. The lwencasting B is indicated as attached to a part C of an inlet lmanifold for an internal combustion engine,

t there being a suitable,-airtight gasket I4 interinterior ofthe nozzle with an annular chamber.. 26. vThe annular chamber 2l surrounding feach Il nozzle is connected by a duct 28 to a centrallylocated bore .30 (Figure ,3) into the lower end of which is threaded amember 32 providing a knife-edged orifice through which communication` is established with the interior of a cylinder 34, having its lower end located slightly above 5 the bottom of the fuel chamber 20.

A piston 36 is located in the cylinder 34 and has a series of ports 38 through which Yfuel is drawn from the fuel'chamber 20 to the nozzles l IB and I8. When the engine is idling the upper 10 ends of ports 38 are substantially `closed by a valve disk 40 having a small orifice 42 which permits of the passage of suilicient fuel for idling of the engine. VWhen the engine is operating at part of full throttle, the valve disk 40 is sucked 15 upwardly away from the upper ends of ports 38 to'permit the flow of additional fuel to the nozzl` I6 and I8.

e piston 36 and cylinder 34 constitute parts of an accelerator pump which is operated ln one 20 direction by a piston rod 44 and in the opposite direction by spring 46. The piston rod 44 rests on one end .of lever 48 plvoted at 50 and having an intermediate portion resting on the cam 52 attached to one end of the throttle valve shaft 2'5 54. I 'he throttle valve shaft 64 is provided with an arm 56 adapted for connection to the usual throttle valve controls.

The throttle valves are shown in the almost closed position which they assume when the en- 30 gine. is idling and in this position of the throttle valves and theirl shaft, the accelerator pumpv piston 38 is in its lowest position. A metering pin.

il `has its enlarged upper end -located in the knifeedged oriiice provided by member 32 when 35 the throttle valve is in the idling position. As the throttle valves are opened, the piston 36 is raised and the tapered upper end of metering pin A58 goes upwardly in theknife-edged oriflce,per

. mitting Va progressively increased space aiording 40' freer flow of fuel tothe nozzles I8 and I8. When r `\the engine is 'operating at full throttle the enlarged upper Aend of metering pin 58 is 'located entirely above the knife-edged oriceto permit maximum flow of fuel to thenozzles. 45 When the throttle is opened uicklythrough an appreciable range -of movement, the piston 36 pumps an additional supply of vfuel to .tiranoszles. If the throttle were opened quickly o ye'r a large range of its movement, too muchi'fuei would- 50 be thus pumped to the` nozzles, and -to prevent.' A this I have provided the plston- 3S' with relief ports i0 whichare normally vclosed by', an-an nu'lai' valve I2- held against the lower l'ends of these ports by spring I4; When the piston ll 55 makes a quick and long upward movement, valve 62 moves away from the lower ends of the ports 66 to permit back iiow of fuel past the piston A66.

The nozzle I8 discharges into a mixing chamf mixing chambers 66 and 68. Intermediate the air horn 16 and the mixing chamber 66 is an air valve 12 consisting of a disk of metal eccentrically mounted on a'shaft 14. A second air valve '16 is located between the air horn 16 and the other' mixing chamber 68. 'Ihe valve 16 is identical with the valve 12 and is similarly mounted on the common shaft 14.

.The common shaft 14 for the two air valves 12 and 16 carries an arm 18 at one end, this arm being connected through link 86 to the piston .82 of an air dashpot cylinder 84. A spring 86 is located in the cylinder 84 and urges the piston 82 upward, thereby tending' to close the air valves 12 and 16, as indicatedin Figure 2. 1

T he particular structure and arrangement of theseair valves and their associated mechanism constitute an important feature of my invention.l The disk air valves 12 and 16 can'be manufactured accurately and economically. The eccentric mounting of these valves provides larger areas on one` side of the mounting shaft than on the other and, since the lower sides of these valves are exposed to the suction in the mixing chambers, theaction of the suction on the larger areasovercomes the action of the suction on the smaller areas and opens these valves against the resistance of the spring 66.

It should be noted that the suction iwtlngzcmV these valves pulls downwardly on the common shaft 14, whereas the reaction of the spring 86 tends t0 lift this shaft. This results ih a. partial balancing of these forces sovthat the shaft 14 is a floating shaft -to the extent that these forces balance. ecause of this balancing, the shaft 14 rests lightly in its bearings and turns easily under all conditionsand without any tendency to bind.

'Ihe mounting of the two air valves 12 and 16 on a commonE shaft alsofhas another. important advantage. Because of manufacturing varia.-

tions inherent in the structure of every air valve.

each air valve has a tendency to flutter at a slightly different period of vibration. `By mounting the two air valves on a common shaft; the.

different-'periods of vibration of thetwo valves dampen or oifset each other and' steadier operation, free from fluttering, results. x A Most of the secondary air admitted past each air valve flows between the right-hand side of the air valve and the opposing wall of the passage in which the air valve is located. "lhe' periphery of this right-hand part of the air valve and the cooperating 4opposing wall constitute a restriction through which the air must pass and produce an effect generally similar to that pro-v duced by a Venturi tube. Becauseot this action, the point in each vmixing chamber where the greatest suction occurs is a short distance below theright-hand side of the associated air valve. and in order to take advantage of this fact. I so arrange the nozzles I6 and |6 that the discharge end of each nomle is-located immediately below its cooperating air valve and atthe'point of approximately greatest suction when the throttle is wide open and very close to the point of greatest suction when the throttle is partly open.

Immediately' below the slr valve shaft 1t r pro- Vvide a metal strip 88 which extends across both mixing chambers and functionsl as a bame to prevent the formationof eddy currents in the mixing chambers. If this baille 86 were not provided, the secondary air rushing by the righthand side `of each air valve would have a tendency to swirl'backwardly and upwardly after a passing. the air valve to satisfy the point of maximum suction formed by this air valve. 'I he location of the baille 88 effectively prevents this swirling or eddying vaction of the air passing the right-hand side of each air valve. This baille 88' -also directs the air passing the left-hand side of each air valve and further constitutes a.means for stabilizing the opening movements of the air valves.

The lower end of each mixing chamber com- -municates with a separate throttle bore and each throttle bore in turn communicates with a separate part .of the manifold C. A separate throtduit 84 which opens' into the throttle bore for the nozzle I8 at a point below the throttle valve located therein. The. conduit 84 has a-needle valve 86 whereby the idling operation of the nozzle I6 may be accurately adjusted.

'I'he nozzle I6 is provided witha series'of radial ports similar to the ports 86 of nozzle I6. and the radial ports of nozzle I8 are in communication with a conduit similar -to conduit 64 but opening into the throttle bore associated with the nozzle I8 and at a point below the throttle valve therein. This conduit is controlled by a needle valve 88 similarto the needle valve 86. By means of needle valves 86 and 88, the idling operation of the nozzles I6 and I6 may be independently adjusted.

'I'he fuel enters the fuel chamber 26 through a pipe |66 leading from the main fuel tank which is located below the chamber. Float |62 is located in the fuel chamber 26 and controls the usual inlet valve |64. The fuel is drawn into the fuel chamber 26 from the main fuel tank by" the suction'maintained in the fuel chamber 26 bythe booster Venturi tube |86.

The booster |66 receives its supply of air through a duct I68-whose inlet end is controlled by a choke plate 'H6 mounted on a pivot II2.

-Choke plate ||6 has an elongated opening ||4 which in the normal pontion of the choke plate Permits free entrance of air into duct |66. As the choke plate II8 is moved from normal running position toward full choke position. the elongated opening 4 progressively restricts the entrance to duct |66 until the full choke position.

Only a very small amount of air is permitted to enter duct |68, thereby reducing the enectlveness 'of booster |66 and facilitating easy starting` of the engine.

The air entering booster |66 from duct |66 into the restricted throat of the booster wherein a suction is created. Radial ports '|I6 connect the interior of this throat with an annular space Ill communicating with upwardly inclined bore |26 whose upper end connects with a horizontal bore |22 leading-*to a downward passage |24 opening into the upper end of fuel chamber 26.

Booster |06 discharges into space |26 which is connected by means of a restricted orifice |20 with a chamber |30 connected with the lower end of each mixing chamber by ducts. |32.

A metering pin |34 reciprocates in a guide |36 and has an enlarged head |30 operatively conncted to an arm |40 rigid with air valve shaft 1 In Figure 3 the parts are shown in the position which they assume when the air valves are ciosed. and in this position the small diameter portieri yof pin |34 is located in orifice |20, thereby providing free discharge for booster |08. As the air valves open under the influence of the suction created in the mixing chambers, the pin |34 is raised to move the tapered portion |42 into the orifice |28 and thereby progressively decreasing the opening through this orifice and correspondingly restricting the discharge of the booster |06 so that the booster always maintains the same degree of suction in the fuel chamber 20 during normal operation of the carburetor. l

The air horn 10 is provided withf an external 4shoulder |44 to facilitate the `attachment of a silencer and air cleaner to the carburetor, if desird.

'The invention disclosed herein is an improvement over Serial No.f7,770, led February 23, 1935. While I have illustrated and described only one embodiment of myy invention, it is to be understood that my invention may` assume various forms and thatthe scope of my invention is to s be limited solely by the following claims.

I claim:

1. In a down draft carburetor of the class described, the combination of a nozzle, a mixing chamber receiving the discharge from said nozzle, an air inlet for said mixing chamber, a valve controlling said inlet, a pivotal mounting for said valve, said mounting having an axis a banie located immediately below said valve and parallel with said axis, said baille 'extending an appreciable distance in thedirection of flow through the mixing chamber to prevent eddying of air passing said valve, and means for supplying fuel to said nozzle.

2. In a down draft carburetor of the class described,`the combination ofa nozzle, a mixing chamber into which said nozzle discharges, an air inlet for said mixing chamber, a disk valve controlling said inlet, a pivotal mounting for said valve, said mounting having an axis, a combined stabilizer and baille located adjacent toand parallel with the axis o f said pivotal mounting upon thesuction side thereof, said stabilizer and baille extending an appreciable distance in the direction of flow through the mixing chamber, and means for supplying fuel to said nozzle.

3. In a carburetor of the class described, the combination of a pair of nozzles, a separate mixing chamber for each nozzle, an inlet for each mixing chamber, a valve for each inlet, a member extending across both inlets on the suction side thereof, said member extending in a plane parallel to the axes of said inlets and constituting a baille for each, and means for supplying fuel to said nozzles.

4. In a down draft carburetor of the class described, the combinationof a mixing chamber, an air inlet for said mixing chamber, a throttle bore constituting an outlet for said mixing chamber, a valve in said inlet, said valve having an eccentric pivotal mounting, a plate having its upper end immediately below said mounting and extending downwardly therefrom to a point as low as the lowest point reached by any portion of said inlet valve. a nozzle discharging into said mixing chamber ata point below said plate and substantially midway between said plate and the wall of said chamber farthest from said plate, and means for supplying fuel to said nozzle.

5. In a carburetor of the class described, the combination of fuel' feeding means,- a pair of valves for admitting secondary air for admixture withl the mixture supplied by said fuel feeding means, a fuel chamber from which'said fuel feeding means draws fuel, a booster for creating a suction in said fuel chamber, means for controlling the degree of suction produced by said booster, and a connection between said lastnamed means and both of said valves whereby the operation of said booster is coordinated with the operation of both of said valves.

ROBERT F. BRACKE. 

